[Fe(diene)(CO)3] complexes as a guide in stereocontrol. Applications to the asymmetric synthesis of natural products
Abstract
The ability of iron tricarbonyl units to control the region- and stereo-chemistry of nucleophilic addition to a neighbouring CX (X = O, N) double bond and 1,5-nucleophilic substitution via a η5-cation intermediate are described. We investigated the potential of acyclic [Fe(diene)(CO)3] complexes as chiral auxiliaries for the asymmetric synthesis of natural products. The asymmetric syntheses of (+) and (–)-frontalin, a hydroxyethylidene dipeptide isostere, a piperidine alkaloid (SS20846A), and N-Boc-O-Me-(2R,3S,5E,7E)-2-aminotetradeca- 5,7-dien-3-ol were achieved by using the stereodirecting ability and mobility of the Fe(diene)(CO)3 group. In addion, we developed an efficient method for synthesizing chiral dienal Fe(CO)3 complexes, which are versatile starting materials for the asymmetric synthesis of the biologically active natural products described above.